Numerical studies on modeling the near- and far-field wake vortex of a quadrotor in forward flight

The operation of Unmanned Aerial Systems (UAS) is expected to keep increasing in the future with its rapid advancement and ever-expanding applications. One of the safety measures that need to be put into place for safe UAS operations is separation requirements. This article presents the results from flow simulations of quadrotor propellers using the Overset method in ANSYS Fluent 19.2 and the Virtual Blade Model (VBM) method in OpenFOAM as part of ongoing work to establish a wake vortex-based safe separation distance for UAS operations. The near-field flow simulation using the Reynolds-averaged Navier-Stokes turbulence model was validated with mesh convergence and turbulence model studies and verified with simulation and experimental data in the literature to ensure that the propeller simulation methods could generate a realistic near-field flow of multi-rotor UAS in forward flight. The far-field flow simulation using the Large Eddy Simulation turbulence model was validated with a mesh convergence study by calculating and comparing the circulation strength of the vortices in the far-field flow of each mesh setup but not verified due to a lack of existing experimental data.